According to the prior art, when integrated circuit components are downsized to achieve a maximum of 0.25μ in the least metal-metal pitch attained by multilayer metal conducting wire manufacturing process technology, the time delay caused by interconnect becomes a major factor in component operation speed, unit area capacity, reliability, and yield. The time delay caused by interconnect equals the product of the resistance of the metal conducting wires and the capacitance of the dielectric layer between the metal conducting wires. Hence, to reduce the time delay caused by interconnect, it is practicable to use a metal of a low resistance or use a material of a low dielectric constant to make the dielectric layer between a metal and another metal.
The silicon dioxide for use in a conventional manufacturing process has a dielectric constant of 3.9 and thus meets the related requirements of a 0.35μ manufacturing process. However, a less-than-0.35μ manufacturing process requires a dielectric layer material of a much lower dielectric constant. Since organic polymeric dielectric materials seldom have a lower dielectric constant than inorganic silicon dioxide and silicon nitride do, organic polymeric dielectric materials are more suitable for use in making metal dielectric layers between multilayer interconnects than inorganic dielectric materials are. In view of this, the present invention provides a novel low dielectric constant material and its manufacturing method.
Dicyclopentadiene (DCPD) is produced when cyclopentadiene undergoes Diels-Alder reaction and thus has an aliphatic structure, high hydrophobicity, and a low dielectric constant materials. A lot of academics and manufacturers introduce DCPD into electronic materials to reduce the dielectric constants thereof. For instance, when catalyzed by aluminum trichloride, it is feasible for DCPD to react with phenol to produce DCPD-phenol oligomer whose structure is depicted as follows:

A wide variety of resins are derived from the phenolic group of the oligomer. In this regard, DIC epoxy resin (HP-7200) is typical of cyanate ester (XU-7187) of Dow-Chemical.
Ueda, an academic, discloses that the double bonds of DCPD undergo a free radical addition reaction with thiol to produce a monomer which carries a functional group, and then synthesize a sulfur-containing material suitable for use in thermoplastic injection molding, wherein the sulfur-containing material exhibits high permeability, high Abbe number, high transmittance, and high glass transition temperature (Suzuki, Y; Higashihara, T.; Ando, S.; Ueda, M. Macromolecules 2012, 45, 3402-3408.)
Wang discloses that a DCPD-phenol oligomer reacts with a phenolic group to produce a benzoxazine resin as compared to BPA-based benzoxazine and a biphenol-based benzoxazine resin. The result shows that the DCPD-based benzoxazine manifests a low dielectric constant and low hygroscopicity and thus is an advantageous material suitable for use in manufacturing advanced printed circuit boards (Hwang, H. J.; Lin, C. Y; Wang, C. S. J. Appl. Polym. Sci 2008, 110, 2413-2423.)
Cyanate ester polymers are well regarded by the electronic sector as high-performance thermosetting resins which display a high glass transition temperature, high thermal stability, low hygroscopicity, and a low dielectric constant when fully cured. The prior art disclosed a lot of novel cyanate esters which contain silicon, trifluoromethyl, phosphorus, and dipentene. Fang discloses introducing various groups into cyanate ester resins to endow them with specific functions which, together with the satisfactory thermal properties of the cyanate esters, attain high thermal stability and high performance (Fang, T.; Shimp, D. A. Prog. Polym. Sci. 1995, 20, 61-118).
In practice, Mitsubishi Gas Chemical Co., Inc. developed a line of copolymer products known as BT-resins and produced from cyanate ester (T: triazine) and bismaleimide (B: bismaleimide). BT-resins share come advantages with polyimide, that is, tolerant to heat, easy to process epoxy resins, and compatible with the other thermosetting resins, such as epoxy resins. However, the market for BT-resins is monopolized by Mitsubishi Gas Chemical Co., Inc. Hence, it is advantageous to develop novel materials with a low dielectric constant in order to circumvent related patents owned by American and Japanese manufacturing giants.
Shackled by a low curing speed and a three-dimensional reticular structure in a late curing stage, cyanate esters manifest high viscosity and thus retention of highly polar terminal group cyanate ester (—OCN), thereby leading to an increase in their dielectric constant. As early as the time when aromatic cyanate esters were developed, academics discovered that cyanate ester (—OCN) reacts with phenol (Ph—OH) to produce imidocarbonate (—OC═NO—). In view of this, Wang discloses reducing the retention of OCN terminal groups by bisphenol-A dicyanate (BADCY) during a polymerization process. Results of experiments conducted by Wang reveal that the reduction of highly polar —OCN terminal groups is effective in reducing the hygroscopicity and dielectric constant, albeit at the cost of some advantages of cyanate esters, including high glass transition temperature and tolerance to high temperature (Shieh, J. Y; Yang, S. P.; Wu, M. F.; Wang, C. S. J Polym Sci Part A: Polym Chem 2004, 42, 2589-2600.)